Center global alerts in v2.

services/web/public/stylesheets/app/editor.less

@@ -60,7 +60,7 @@
 		display: inline-block;
 		text-align: left;
 		min-width: 400px;
-		padding: (@line-height-computed / 4);
+		padding: @global-alerts-padding;
 		font-size: 14px;
 		margin-bottom: (@line-height-computed / 4);
 		position: relative;

services/web/public/stylesheets/core/_common-variables.less

@@ -909,6 +909,7 @@
 @project-name-color              : @gray;
 @project-rename-link-color       : @gray-light;
 @project-rename-link-color-hover : @gray-dark;
+@global-alerts-padding           : (@line-height-computed / 4);
 
 // Editor file-tree
 @file-tree-bg                    : transparent;

services/web/public/stylesheets/core/ol-variables.less

@@ -210,6 +210,7 @@
 @project-name-color               : @ol-blue-gray-2;
 @project-rename-link-color        : @ol-blue-gray-2;
 @project-rename-link-color-hover  : @ol-blue-gray-1;
+@global-alerts-padding            : 7px;
 
 // Editor file-tree
 @file-tree-bg                   : @ol-blue-gray-4;